Noradrenergic enhancement of associative fear memory in humans.

Abstract

Ample evidence in animals and humans supports the noradrenergic modulation in the formation of emotional memory. However, in humans the effects of stress on emotional memory are traditionally investigated by declarative memory tests (e.g., recall, recognition) for non-associative emotional stimuli (e.g., stories, pictures). Given that anxiety disorders are thought to originate from associative learning processes and are characterized by distressing emotional responses, the existing literature seems to be inconclusive for the understanding of these disorders. Here, we tested whether noradrenaline strengthens the emotional expression of associative fear memory by using a differential fear conditioning procedure in humans. Stimulation of the noradrenergic system by the administration of yohimbine HCl (20mg) during memory formation did not directly augment the differential startle fear response 48 h later. Yet, the other retention tests uncovered that the administration of yohimbine HCl contrary to placebo pill extensively delayed the process of extinction learning and generated a superior recovery of fear (i.e., reinstatement and reacquisition). Conversely, the yohimbine HCl manipulation did not affect the skin conductance responding and the US expectancy ratings, emphasizing the concept of multiple memory systems. To our knowledge this is the first demonstration in humans that increased noradrenaline release during or shortly after a stressful event strengthens the formation of associative fear memory traces. The present findings suggest that noradrenaline may play an important role in the etiology and maintenance of anxiety disorders.

• Authors: Marieke Soeter, Merel Kindt
• Journal: Neurobiology of learning and memory (Neurobiol Learn Mem) Vol. 96 Issue 2 Pg. 263-71 (Sep 2011) ISSN: 1095-9564 [Electronic] United States
• PMID: 21624479 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2011 Elsevier Inc. All rights reserved.

Chemical References

• Adrenergic alpha-2 Receptor Antagonists
• Yohimbine
• Salivary alpha-Amylases
• Norepinephrine

Topics

• Adolescent
• Adrenergic alpha-2 Receptor Antagonists (pharmacology)
• Adult
• Association Learning (drug effects, physiology)
• Conditioning, Psychological (drug effects, physiology)
• Emotions (drug effects, physiology)
• Fear (drug effects, physiology)
• Female
• Galvanic Skin Response (drug effects, physiology)
• Humans
• Male
• Memory (drug effects, physiology)
• Norepinephrine (physiology)
• Reflex, Startle (drug effects, physiology)
• Saliva (metabolism)
• Salivary alpha-Amylases (metabolism)
• Yohimbine (pharmacology)